There are presently a number of methods and techniques for the treatment of cancer, among which may be included: radiation therapy, chemotherapy, immunotherapy, and surgery. The common characteristic for all of these techniques as well as most other presently known techniques is that they are extracellular in scope, that is, the cancer cell is attacked and attempted to be killed through application of the killing force or medium outside of the cell.
The extracellular approach is found to be less effective and efficient because of the difficulties of penetrating the tough outer membrane of the cancer cell that is composed of two protein layers with a lipid layer in between. Of even greater significance is that to overcome the protection afforded the cell by the cell membrane in any extracellular technique, the attack on the cancer cells must be of such intesity that considerable damage is caused to the normal cells resulting in severe side effects upon the patient. These side effects have been found to limit considerably the effectiveness and usefulness of these treatments.
A safe and effective cancer treatment has been the goal of investigators for a substantial period of time. Such a technique, to be successful in the destruction of the cancer cells, must be selective in effect upon the cancer cells and produce no irreversible damage to the normal cells. In sum, cancer treatment must selectively differentiate cancer cells from normal cells and must selectively weaken or kill the cancer cells without affecting the normal cells as described in U.S. Pat. No. 4,106,488.
It has been known that there are certain physical differences that exist between cancer cells and normal cells. One primary physical difference that exists is in the temperature differential characteristics between the cancer cells and the normal cells. Cancer cells, because of their higher rates of metabolism, have higher resting temperatures compared to normal cells. In the living cell, the normal temperature of the cancer cell is known to be 37.5.degree. Centigrade, while that of the normal cell is 37.degree. Centigrade. Another physical characteristic that differentiates the cancer cells from the normal cells is that cancer cells die at lower temperatures than do normal cells. The temperature at which a normal cell will be killed and thereby irreversibly will be unable to perform normal cell functions is a temperature of 46.5.degree. Centigrade, on the average. The cancer cell, in contrast, will be killed at the lower temperature of 45.5.degree. Centigrade. The temperature elevation increment necessary to cause death in the cancer cell is determined to be at least approximately 8.0.degree. Centigrade, while the normal cell can withstand a temperature increase of at least 9.5.degree. Centigrade.
It is known, therefore, that with a given precisely controlled increment of heat, the cancer cells can be selectively destroyed before the death of the normal cells. On the basis of this known differential in temperature characteristics, a number of extracellular attempts have been made to treat cancer by heating the cancer cells in the body. This concept of treatment is referred to as hyperthermia. To achieve these higher temperatures in the cancer cells, researchers have attempted a number of methods including inducing high fevers, utilizing hot baths, diathermy, applying hot wax, and even the implantation of various heating devices in the area of the cancer.
At this time, none of the extracellular approaches to treat cancer have been truly effective and all have the common characteristic of approaching the problem by treating the cancer cell extracellularly. The outer membrane of the cancer cell, being composed of lipids and proteins, is a poor thermal conductor, thus making it difficult for the application of heat by external means to penetrate into the interior of the cell where the intracellular temperature must be raised to effect the death of the cell. If, through the extracellular approaches of the prior hyperthermia techniques, the temperatures were raised so high as to effect an adequate intracellular temperature to kill the cancer cells, many of the normal cells adjacent to the application of heat could very well be destroyed.